In recent years, small and medium-sized printing companies have eliminated copper-zinc plates that are heavily polluted, cumbersome to operate and whose quality should not be controlled. In addition to the bronzing of trademarks, hardcover covers, packaging and decoration, copper-zinc plates are also used, and other letterpress printing is not required. Both plastic and bill printing have adopted a solid resin plate with a simple plate making procedure, a short plate making cycle, good ink transfer performance, light weight, and no pollution, and a high printing resistance.

In the process of resin plate making, problems such as small words or small dot peeling and thin line bending are prone to occur. The field version has uneven layout, uneven ink, spotted spots, and a resin plate with a screen size of 90 lines/inch or more. Observe the drawbacks of dot size. The above problems are related to the exposure time of the resin plate during the plate making process, the negative contrast of the positive image negative film, the fogging of the light-transmitting portion, the unevenness of the resin plate surface, and the surface coloration. The following will analyze in detail the causes of these problems and solutions.

Small text, lines, dots are missing

Thin line bending and fine text, dot exfoliation may be caused by the following reasons: 1 resin plate exposure time is insufficient; 2 film contrast is small, graphic is not clear, there is fog; 3 resin plate thermal curing process (baked version) is not appropriate; 4 The resin plate has a low temperature of the developing water and a long flushing time; the brush is hard and the printed plate is dark; 5 the printing pressure on the machine is high and the adjustment is improper. The solution is as follows.

1 First, it is necessary to grasp the correct exposure time. When encountering small texts, lines, patterns, or small dots, you should use a 3kW iodine lamp for exposure for about 20 minutes, which is longer than the normal exposure time, so that the small text and lines It will not fall off. The exposure time is long, and the lateral slope of the resin plate produced by the system is relatively good, reaching about 70°.

2 have a perfect darkroom technology. The film contrast should be as large as possible, no fog, text, lines smooth, smooth, no lack of pen off, and to master the exposure, development, fixing time and temperature of the film.

3 Whether it is used for automatic brush plate printing with solid resin platesetters or manual brush plate printing, the water temperature must not be too low. It is best to wash at a water temperature of 50-60°C until the substrate is revealed. It is better to choose a brush with a soft bristles, and brush it slightly when flushing, as long as it has a certain depth. In addition, the brush plate cleaning time should not be too long, the drying and thermal curing process is generally carried out in an electric oven, drying at a temperature of 60 ~ 80 °C, evaporation of the water on the plate surface, pay attention to prevent the drying temperature is too high, The occurrence of resin blistering on the plate surface.

4 Without pressure, the ink cannot be transferred to the paper, but the embossing force must be moderate. When the resin plate is printed on the machine, the pressure of the ink roller must be adjusted, and the pressure between the resin plate and the platen roller should be as small as possible under the premise of guaranteeing the printing quality, so as to avoid the fine text, lines, and texts caused by excessive pressure. Dropping or crushing weakens the resistance of the resin plate. Magnetic plates and aluminum plates are preferred because of their uniform thickness, flat layout, and relatively easy pressure adjustment. The flatness of the wood is relatively poor, it is easy to convex after being pressed, and it is deformed by water.

Uneven layout, paste version

The solid version (text, lines, and hollow version) that are printed with a resin plate, often suffer from uneven layout and stencil problems. The reasons are various. The layout is uneven and the photosensitive film coating is uneven. The reason is that there are reasons why the process operation is not proper. Before the resin plate is exposed, a small amount of talcum powder should be rubbed to avoid air gaps between the film and the resin plate surface. Slab printing machine vacuum pump suction to be strong, the film and the resin plate close to the surface of the photosensitive film to be closely matched, so as to reduce the problem of surface unevenness. When there are patterns or scars after development of the resin plate, it can also be lightly rubbed with the grinding carbon of the original copper-zinc plates, and the pattern and scratches can be removed, so that the surface is flat and the resin plate is inked. Will be more uniform, the effect will be better.

When printing a solid version or a hollow version with fine text and lines, the exposure time should be reduced correspondingly, so as to avoid the problem of insufficient brushing and deep flushing during flushing. Resin version of the hollow text, lines, patterns should be considered in the design of paste problem, the design of ink lines and text should be thicker, so as to avoid the resin version of the machine printing, ink color paste version, ink too small problem . In addition, the vacuum pump suction during printing should be real, the darkroom technology should be perfect, the bottom plate contrast should be large, should be clear, clean, no fog, to ensure that not paste version, to meet the resin printing quality requirements.

It is not easy to observe outlets when printing

Before the exposure of the domestic solid resin plate, the layout was green or pale yellow, and the green resin plate was predominant. After exposure, the resin plate is old yellow and yellow, which is the color that the human's vision is most difficult to observe. When squeezing a 90-line/inch dot plate, it is not easy to observe the size of the dots, which makes it difficult to control the depth, slope, and quality of the cable version of the plate. It is best to add some non-toxic, odorless, non-polluting dyes or colorants, such as methyl violet and other colorants, to the darker colors such as green, red, and blue on the surface of the photosensitive solid resin plate or the photosensitive film. It is better to observe the situation of dots when making a plate, so as to achieve the purpose of controlling the depth and effect of the plate.


Xin County, Hubei Province Printing Factory Wang Xincheng
Source: "Printing Technology - Equipment and Special Printing